Recognizing that minimizing cost in manufacturing environment-friendly products is important to improve the competitiveness, many companies and countries in the world make efforts to design buildings having high energy efficiency. Also, many companies and countries intensively compete each other to have priority in technologies to provide zero-energy buildings that do not depend on external energy. There are various certification systems to certify environment-friendly buildings and energy efficient buildings for buildings that meet certain requirements. In addition, the standard for insulation performance of windows and walls becomes hightened. Further, there are recent worldwide trends that collective energy consumption management systems are being effective and zero-energy buildings are being required. In view of these, it is widely recognized that environment-friendly green technology based business will produce high profit and developing and protecting related technologies is important.
It is known that a substantial amount (at least 50%) of energy can be saved by insulating the outer walls and windows of a building. Insulating outer walls and windows are thus regarded as one of the most important factors in saving energy of a building.
Conventionally, CFC, polyurethane foam, styro foam, glass wool, and the like were used as an insulation material in construction industry. Recently, vacuum insulation panel (VIP) and aerogel have been proposed. A vacuum insulation panel filled with glass wool was reported to show insulation performance at least 16 times higher than that of glass wool and at least 10 times higher than that of polyurethane foam or styro foam. Typically, a vacuum insulation panel includes a masking plate made of a metal or acid resistant plastic to maintain vacuum state inside the panel and a filler filled in the panel to maintain the shape of the panel. The fillers are made of organic or inorganic powders, fibers, or high molecular weight resins are. These materials, however, have disadvantages that they may cause environmental harm after use and they may reduce insulation performance of the panels due to increased pressure by the gas produced by the materials.
Compared with conventional insulation panels, conventional vacuum insulation panels show higher insulation performance, fire resistancy, thermal resistancy, recyclability, and sound-proofing performance. The conventional vacuum insulation panels, however, are expensive, heavy, limited in size (30 cm×30 cm), and show low insulation performance at joints of panels.
Korean Patent No. 0253841 discloses an insulation jacket of a low-temperature device and a method of producing the same. Insulation materials such as glass wool, synthetic resin, polyurethane, organic polymers or multi-layers are filled in a vacuumed space inside the jacket and PdO is disposed in the vacuumed space to absorb hydrogen. Also, getter material is used to absorb gas effectively and zeolite is used to absorb water.
Korean Patent No. 0188443 discloses a vacuum insulation panel. A filler is filled in a vacuumed space and barium-lithium alloy, as a getter material, is inserted into the filler to adsorb gas. The patent describes that the gas pressure that the vacuum insulation panel can achieve is 0.1˜10mmHg Korean Patent Application No. 10-1998-0710788 discloses a vacuum insulation container and a method of making the same. The vacuum insulation container includes a metal outer jacket having a vacuum discharge tube therein, a filler made of glass wool filled in the vacuumed space inside the jacket, and a getter system (SAES GETTERS, ST301) to absorb gas.
Korean Patent No. 0466614 discloses a method of preparing an open-cell hard polyurethane foam and a vacuum insulation panel using the same. According to the method, hard polyurethane foam, as a filler, is inserted into a metal laminate film
Korean Patent No. 0540522 discloses a vacuum insulation panel and a device using the same.
Sheets each made of SiO2 as a main component and Al2O3, CaO, and MgO are stacked to form a filler. The filler is filled in an outer panel having gas masking capability. The outer panel is an aluminum-laminate film and filled with a filler and a gas adsorber is provide with the filler inside the panel.
Korean Patent Application No. 10-2004-7019549 discloses a vacuum insulation panel, a method of preparing same, and a refrigerator using the same. A filler made in the form of plate and with fiber is filled in an outer panel having gas masking capability. The panel is provided with, in addition to the filler, a physical adsorbing agent and chemical adsorbing agent to adsorb water and a chemical adsorber (non-vaporizable getters) to adsorb gas. The outer panel is a metal thin layer made of, e.g., stainless steel, aluminum, and iron, or is a plastic film laminate.
Korean Patent No. 0775716 discloses vacuum insulation material and a method of making the same. The vacuum insulation material is formed by a plurality of fillers having an octagonal shape and being made of glass fibers. The fillers are covered by an outer panel. The inner side of the panel is vacuum discharged. While decompressing the fillers, the outer panel is heat compressed, thereby thermally fusing the fillers and outer panel. As a result, the thermal fused portion is formed along the portion of the fillers.
Korean Patent Application No. 10-2006-0037124 discloses a vacuum insulation material and a method of preparing the same. A gas bather film having a layer of thermal fusion is used as an outer material. A filler is filled in the gas barrier film. Thereafter, a vacuum discharge is performed and the insulation material is sealed.
Korean Patent Application No. 10-2009-0076463 discloses a vacuum insulation material, an insulation box using the same, and a refrigerator using the same. A filler made of organic fibers is filled in an outer material having gas masking capability. A getter material to adsorb gas or steamed water is provide in the outer material. A filler made of polystyrene resin is proposed.
Korean Patent Application No. 10-2006-0037124 discloses a vacuum insulation material and a method of making the same. Gas barrier films are stacked and the edges of the films are folded in. Even when micropores and cracks are formed on the films, external gas cannot be introduced and the degree of vacuum is not lowered. The vacuum insulation material can be mounted to an object having a complicated shape.
Korean Patent No. 0753720 discloses a vacuum insulation material and a method of making the same. An outer material having gas masking capability is filled with a filler made of inorganic fiber polymers that do not contain binders.
Korean Patent No. 0781010 discloses a vacuum insulation material and a method of making the same. An outer film is filled with fiber glass and the inner side of the outer film is vacuum discharged. A portion that can be folded is provided, thereyby allowing the film and the filler to be folded.
Korean Utility Model Registration Nos. 0414340 and 0415600 disclose a vacuum insulation panel that is formed by stacking a plurality of plates having continuous, consistent waves or embossed wrinkles with a flat panel. The edges thereof are stitched and finished with sealers, thereby forming vacuum spaces. A part of the stitched portion is finished with silicone and a needle is inserted into the silicone, thereby allowing the needle to act as a discharge tube.
The above-described prior art still has problems, however. The purpose of filling a filler in an insulating medium is to maintain the shape of an outer material and perform the insulation function.
The fillers can limit the insulation function.
The fillers reduce the degree of vacuum inside the outer material. Even when a filler having low thermal conductivity, the filler causes thermal transfer. It is known that when a filler is filled, the maximum degree of vacuum is ones or tens torr because low conductance of the filler and degasification occurred due to the filler at discharge. The above-described prior art merely describes that tens torr could be achieved or gas pressure could be lowered.
It is known that when the gas pressure is 10−2 torr, the theoretical maximum thermal conductivity is 0.002 W/mK. In reality, as the gas pressure is ones or tens torr, thermal transfer by convection and thermal transfer by conduction of fillers, the thermal conductivity may be much far higher than 0.002 W/mK.
FIG. 23 shows the relationship between thermal conductivity and gas pressure where an inorganic powder insulation filler is filled. The relationship shows that vacuum pressure should be maintained at 10−2 torr or lower to attain maximum insulation performance. Even though the relationship may vary slightly depending on the type/kind of the filler and compression density, it will be similar to that shown in FIG. 23. As shown in FIG. 23, in case where a filler is filled in an outer material, even if the vacuum pressure is maintained at 10−2 torr or lower, thermal transfer by conduction by the filler occurs, causing the thermal conductivity to be much higher than 0.002 W/mK. Accordingly, in case of using a filler, it is difficult to reduce the pressure that causes thermal loss due to convection and it is difficult to avoid thermal loss due to thermal conduction by the filler.
Thermal transfer in a vacuumed space from a heat source to ambient depends on the degree of vacuum. Although the thermal transfer may vary slightly depending on the shape of the heat source, the distance between the heat source and an object, and the shape of the object, it will be similar to that shown in FIG. 24. Thermal transfer occurs by radiation and convection by remaining gas. The main mechanism of thermal transfer with respect to vacuum regions I to III of FIG. 24 is as follows.
Vacuum region I: radiation and convection
Vacuum region II: convection (depending on degree of vacuum)
Vacuum region III: radiation
In case of a vacuum insulation panel in which a filler is filled in an outer panel, thermal transfer through the vacuum insulation panel occurs by radiation, convection by remaining gas, and conduction by the filler. The dependency of thermal transfer on degree of vacuum is shown in FIGS. 23 and 24. The main mechanism of thermal transfer with respect to vacuum regions I to III of FIG. 24 in case of the vacuum insulation panel in which a filler is filled in an outer panel is as follows.
Vacuum region I: Convection and conduction
Vacuum region II: Convection and conduction (thermal transfer by convection depends on degree of vacuum; compared with vacuumed space, as thermal transfer by convection occurs less, change of thermal transfer is not that high in this region)
Vacuum region III: Conduction
Some conventional vacuum insulation panels have non-diffusion getters to maintain vacuumed state and/or separate water adsorbing agent. In case of vacuum insulation panels using non-diffusion getters, cross sectional adsorption area is not enough and activation rate necessary for re-adsorption is low.
Some conventional vacuum insulation panels have an outer panel which is a plastic film or a thin plate made of stainless steel, aluminum, iron, etc. As a result, when a discharge process is performed after a filler is filled, the outer panel is compressed as the shape of the filler. Some other conventional vacuum insulation panels require separate compression process to bond an outer panel and a filler. In some conventional vacuum insulation panels, to hemetically seal the outer panel, sealers are used to bond the edges of the outer panel or the edges are folded and compressed. In case of sealers, degasification occurs due to the sealers, which in turn reduces the degree of vacuum. Further, when the panel is exposed to an external environment, the bonding force is reduced, which in turn reduces the degree of vacuum. In addition, in case of folding and compressing the edges, it is hard to attain sufficient degree of vacuum. It thus needs a method of bonding the edges of the outer panel to ensure hemetic sealing and maintain vacuum pressure of 10−3 torr or lower.
Some vacuum insulation panels include a filler inside an outer panel. Because of the filler filled in, it is difficult to reduce the pressure that causes thermal loss by convection and it is hard to avoid thermal loss by conduction by the filler itself.
The above information disclosed in the Background Art section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.